Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
nasai-kubra:10465 – ʿUbaydullāh b. Saʿd b. Ibrāhīm b. Saʿd from my uncle from my father > Ibn Isḥāq > al-Ḥārith b. Fuḍayl al-Anṣārī > Muḥammad b. Muslim al-Zuhrī > Ḥumayd b. ʿAbd al-Raḥman b. ʿAwf

[Machine] "A group of the companions of the Prophet ﷺ told him that they heard the Messenger of Allah ﷺ saying, 'Say: He is Allah, [who is] One' [Surah Al-Ikhlas, verse 1]. It is equivalent to one-third of the Quran for those who recite it in their prayer."  

الكبرى للنسائي:١٠٤٦٥ – أَخْبَرَنَا عُبَيْدُ اللهِ بْنُ سَعْدِ بْنِ إِبْرَاهِيمَ بْنِ سَعْدٍ قَالَ حَدَّثَنَا عَمِّي قَالَ حَدَّثَنَا أَبِي عَنِ ابْنِ إِسْحَاقَ قَالَ حَدَّثَنِي الْحَارِثُ بْنُ فُضَيْلٍ الْأَنْصَارِيُّ عَنْ مُحَمَّدِ بْنِ مُسْلِمٍ الزُّهْرِيِّ قَالَ أَخْبَرَنِي حُمَيْدُ بْنُ عَبْدِ الرَّحْمَنِ بْنِ عَوْفٍ

أَنَّ نَفَرًا مِنْ أَصْحَابِ النَّبِيِّ ﷺ حَدَّثُوهُ أَنَّهُمْ سَمِعُوا رَسُولَ اللهِ ﷺ يَقُولُ {قُلْ هُوَ اللهُ أَحَدٌ} [الإخلاص 1] لَتَعْدِلُ ثُلُثَ الْقُرْآنِ لِمَنْ صَلَّى بِهَا  

See similar narrations below:

Collected by Nasāʾī's Kubrá
nasai-kubra:10441 – Qutaybah b. Saʿīd > Ḥammād > ʿĀṣim > Zir > Ibn Masʿūd

"Qul Huwa Allahu ahad [Say: He is Allah, (the) One] is equivalent to one third of the Quran." (Using translation from Ibn Mājah 3787)   

الكبرى للنسائي:١٠٤٤١ – أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ قَالَ حَدَّثَنَا حَمَّادٌ عَنْ عَاصِمٍ عَنْ زِرٍّ عَنِ ابْنِ مَسْعُودٍ قَالَ

{قُلْ هُوَ اللهُ أَحَدٌ} [الإخلاص 1] تَعْدِلُ ثُلُثَ الْقُرْآنِ  

nasai-kubra:10455 – Aḥmad b. Sulaymān > Yaʿlá > Zakariyyā > ʿĀmir > ʿAbd al-Raḥman b. Abū Laylá > Abū Ayyūb al-Anṣārī

"Qul Huwa Allahu ahad [Say: He is Allah, (the) One] is equivalent to one third of the Quran." (Using translation from Ibn Mājah 3787)   

الكبرى للنسائي:١٠٤٥٥ – أَخْبَرَنَا أَحْمَدُ بْنُ سُلَيْمَانَ قَالَ حَدَّثَنَا يَعْلَى قَالَ حَدَّثَنَا زَكَرِيَّا عَنْ عَامِرٍ عَنْ عَبْدِ الرَّحْمَنِ بْنِ أَبِي لَيْلَى عَنْ أَبِي أَيُّوبَ الْأَنْصَارِيِّ قَالَ

{قُلْ هُوَ اللهُ أَحَدٌ} [الإخلاص 1] تَعْدِلُ ثُلُثَ الْقُرْآنِ